How to convert Android content url and use it to open file?

Hitokage

Hey, I am using FileDialog in QML to pick a file on Android but the path I get is in this content:// format. Is there any way to convert this and use it for example as QFile url? Right now I'm getting (even after using toLocalFile() from QUrl ):

Filename: "content://com.android.providers.downloads.documents/document/381"
QFSFileEngine::open: No file name specified

Working on a multiplatform mobile app so I'd like to be able to use this at least on iOS too.
Thanks!

EDIT: Since FileDialog seems to be having more problems in Android right now I have created my own file picker using FolderListModel and StandardPaths. It's not an answer to this question but it is probably safer solution that works on all platforms.

sierdzio

You need a file provider which will translate the file name into something that Java (or C++) backend can understand. Unfortunately it's platform-specific and quite complicated. My answer to this question might help, although it's incomplete (sorry!).

J.Hilk

@Hitokage I would suggest taking a look at this blog post:

https://www.qt.io/blog/2017/12/01/sharing-files-android-ios-qt-app

It is a rather in-depth post with working code that sends and receives files. It's not perfect but very good, you should be able to adapt it easily enough 😉

Hitokage

@J-Hilk @sierdzio thank you guys!

R-Type

with Qt 5.15.2 I can open and read content:// path directly passing it to QFile. According to this it is possible since Qt 5.13.

mahdi.ze

you can use CrossQFile. CrossQFile is a QFile that supports android uri.
https://github.com/mahdize/CrossQFile

Soviet-Ball

@Hitokage
Hi,
you can try this function below.
(I use class QJniObject in Qt6, just replace it with QAndroidJniObject :D)

static QString getRealPathFromUri(const QUrl &url)
{
    QString path = "";

    QFileInfo info = QFileInfo(url.toString());
    if(info.isFile())
    {
        QString abs = QFileInfo(url.toString()).absoluteFilePath();
        if(!abs.isEmpty() && abs != url.toString() && QFileInfo(abs).isFile())
        {
            return abs;
        }
    }
    else if(info.isDir())
    {
        QString abs = QFileInfo(url.toString()).absolutePath();
        if(!abs.isEmpty() && abs != url.toString() && QFileInfo(abs).isDir())
        {
            return abs;
        }
    }
    QString localfile = url.toLocalFile();
    if((QFileInfo(localfile).isFile() || QFileInfo(localfile).isDir()) && localfile != url.toString())
    {
        return localfile;
    }
#ifdef Q_OS_ANDROID
    QJniObject jUrl = QJniObject::fromString(url.toString());
    QJniObject jContext = QtAndroidPrivate::context();
    QJniObject jContentResolver = jContext.callObjectMethod("getContentResolver", "()Landroid/content/ContentResolver;");
    QJniObject jUri = QJniObject::callStaticObjectMethod("android/net/Uri", "parse", "(Ljava/lang/String;)Landroid/net/Uri;", jUrl.object<jstring>());
    QJniObject jCursor = jContentResolver.callObjectMethod("query", "(Landroid/net/Uri;[Ljava/lang/String;Ljava/lang/String;[Ljava/lang/String;Ljava/lang/String;)Landroid/database/Cursor;", jUri.object<jobject>(), nullptr, nullptr, nullptr, nullptr);
    QJniObject jScheme = jUri.callObjectMethod("getScheme", "()Ljava/lang/String;");
    QJniObject authority;
    if(jScheme.isValid())
    {
        authority = jUri.callObjectMethod("getAuthority", "()Ljava/lang/String;");
    }
    if(authority.isValid() && authority.toString() == "com.android.externalstorage.documents")
    {
        QJniObject jPath = jUri.callObjectMethod("getPath", "()Ljava/lang/String;");
        path = jPath.toString();
    }
    else if(jCursor.isValid() && jCursor.callMethod<jboolean>("moveToFirst"))
    {
        QJniObject jColumnIndex = QJniObject::fromString("_data");
        jint columnIndex = jCursor.callMethod<jint>("getColumnIndexOrThrow", "(Ljava/lang/String;)I", jColumnIndex.object<jstring>());
        QJniObject jRealPath = jCursor.callObjectMethod("getString", "(I)Ljava/lang/String;", columnIndex);
        path = jRealPath.toString();
        if(authority.isValid() && authority.toString().startsWith("com.android.providers") && !url.toString().startsWith("content://media/external/"))
        {
            QStringList list = path.split(":");
            if(list.count() == 2)
            {
                QString type = list.at(0);
                QString id = list.at(1);
                if(type == "image")
                    type = type + "s";
                if(type == "document" || type == "documents")
                    type = "file";
                if(type == "msf")
                    type = "downloads";
                if(QList<QString>({"images","video","audio"}).contains(type))
                    type = type + "/media";
                path = "content://media/external/"+type;
                path = path + "/" + id;
                return getRealPathFromUri(path);
            }
        }
    }
    else
    {
        QJniObject jPath = jUri.callObjectMethod("getPath", "()Ljava/lang/String;");
        path = jPath.toString();
        qDebug() << QFile::exists(path) <<path;
    }

    if(path.startsWith("primary:"))
    {
        path = path.remove(0,QString("primary:").length());
        path = "/sdcard/" + path;
    }
    else if(path.startsWith("/document/primary:"))
    {
        path = path.remove(0,QString("/document/primary:").length());
        path = "/sdcard/" + path;
    }
    else if(path.startsWith("/tree/primary:"))
    {
        path = path.remove(0,QString("/tree/primary:").length());
        path = "/sdcard/" + path;
    }
    else if(path.startsWith("/storage/emulated/0/"))
    {
        path = path.remove(0,QString("/storage/emulated/0/").length());
        path = "/sdcard/" + path;
    }
    else if(path.startsWith("/tree//"))
    {
        path = path.remove(0,QString("/tree//").length());
        path = "/" + path;
    }
    if(!QFileInfo(path).isFile() && !QFileInfo(path).isDir() && !path.startsWith("/data"))
        return url.toString();
    return path;
#else
    return url.toString();
#endif

}

ekkescorner

@Soviet-Ball you don't need this anmore in Qt 6.6:
FileDialog on Android supports content URLs.

QFileInfo().fileName()

gives you the file path
so easy now :)

shokarta

@ekkescorner how does it gives me path? as of 6.7.2 it gives only the proper filename...
so i still dont know where the file is stored in order to open it :/

ekkescorner

@shokarta try with Android FileDialog

FileDialog {
    title: qsTr("Select a File")
    fileMode: FileDialog.OpenFile
    onAccepted: {
    if(selectedFiles.length) {
         console.log("we selected: ", selectedFiles[0])

Selected File 'München.pdf' from FileDialog
...this gives you per ex:

content://com.android.providers.downloads.documents/document/32

// you can check from C++ and verify fileUrl:

QFileInfo fileInfo(fileUrl);
qDebug() << "verifying fileUrl: " << fileUrl;
qDebug() << "BASE: " << fileInfo.baseName();
qDebug() << "FileName: " << fileInfo.fileName();
qDebug() << "Path: " << fileInfo.path();
qDebug() << "absoluteFilePath: " << fileInfo.absoluteFilePath();
return fileInfo.exists();

this gives you:

verifying fileUrl:  "content://com.android.providers.downloads.documents/document/32"
BASE:  "München"
FileName:  "München.pdf"
Path:  "content://com.android.providers.downloads.documents/document" 
absoluteFilePath:  "content://com.android.providers.downloads.documents/document/32"
file exists